1. Field of the Invention
The present invention relates to the formation of element-free spaces or gaps in slide fastener chains having intermeshing rows of continuous filamentary coupling elements sewn to confronting longitudinal edges of slide fastener stringer tapes.
2. Description of the Prior Art
There is known an apparatus for gapping a slide fastener chain by cutting interdigitating rows of helically coiled coupling elements over a length and pushing upwardly the severed coupling elements off their stringer tapes to thereby form an element-free space or gap equal to the length (Japanese Laid-Open Patent Publication No. 56-156104 published on Dec. 2, 1981). More specifically, the disclosed apparatus has upper and lower grippers for gripping the stringer tapes and a cutter blade movable toward a lower die for thrusting into the length of intermeshing coupling elements placed against the lower die to cut off upper legs of the coupling elements above coupling heads thereof. After the desired upper legs of the coupling elements have been cut off, a knockout blade is moved upwardly between the stringer tapes across the horizontal plane thereof to forcibly remove the severed coupling elements off sewing stitches on the stringer tapes.
The above conventional gapping apparatus has the following disadvantages: Since the upper legs of desired coupling elements are severed by the cutter blade having a single cutting edge, the cut edges of the coupling elements are relatively remote from the sewing stitches by which the coupling elements are fastened to the stringer tapes. Additionally, the severed coupling elements are moved merely upwardly by the knockout blade until they are freed from the stringer tapes. Under such conditions, a large force has to be imposed by the knockout blade on the cut-off coupling elements to remove them from the stringer tapes, with the result that the sewing stitches and/or the stringer tapes are likely to be torn apart or otherwise damaged under undue forces.
Another chain gapping apparatus is disclosed in Japanese Patent Publication No. 45-297 published on Jan. 8, 1970. The chain gapping apparatus also has upper and lower grippers for gripping stringer tapes and a flat punch movable toward cutter blades for pressing a length of intermeshing coupling elements against the cutter blades to cut off lower legs of the coupling elements below coupling heads thereof. In the gapping apparatus of the disclosed type, the punch has a flat or arcuate lower end surface for contacting the coupling elements. When the punch presses the length of coupling elements against the cutter blades, the coupling elements are apt to slip longitudinally against the flat lower surface of the punch, thus failing to position the slide fastener chain with respect to the punch in forming a gap or space in the slide fastener chain. The punch causes another problem at the time of removing the severed coupling elements off the stringer tapes by depressing the punch and the cutter blades with the severed coupling elements sandwiched therebetween. During the downward movement of the punch and the cutter blades, the severed coupling elements are likely to move longitudinally with respect to the punch and the cutter blades. As a result, some severed coupling elements at an end of the gap to be formed are displaced out of engagement with the punch and the cutter blades and will remain unremoved on the stringer tapes.